Am'ju<iyr'i9519arn1'  J      Purtty  of  Commercial  Aspirin.  467 
odor,  while  others  where  the  bromine  value  is  high  give  a  slight 
suggestion. 
In  the  three  exceptions  (4,  9,  10),  which  might  fall  in  with  the 
above  statement  regarding  the  acid  exceeding  the  bromine  value, 
the  excess  acid  is  considerably  greater  than  that  due  to  dissociation, 
as  indicated  by  the  iron  test,  thus  confirming  from  another  point  of 
view  what  has  been  said  above  regarding  the  occurrence  of  an  acid- 
ity not  due  to  acetyl-salicylic  acid.  This  "excess"  acidity  is  not  open 
to  any  ready  or  easily  demonstrable  explanation,  but  the  presence 
of  such  a  body  as  salicyl-acetic  acid,  C6H4-6-COOH  CH2-COOH, 
in  which  there  are  two  carboxyl  to  but  one  salicylic  group,  is  very 
suggestive.  With  a  chemical  like  aspirin,  where  a  number  of  sec- 
ondary products  are  possible,  quite  apart  from  real  extraneous  im- 
purities, in  the  absence  of  specific  reactions  it  is  largely  a  matter  of 
conjecture  what  the  precise  substances  are  that  cause  the  variations 
in  the  analytical  figures  with  different  samples.  That  there  are 
traces  of  other  impurities  present  in  some  samples  is  certain,  the 
peculiar  odors  in  the  crystals  or  powder  frequently  developed  by 
treating  with  solvents  and  with  alkali,  and  the  different  intensity  in 
color  of  the  caustic  and  carbonate  of  soda  solution  all  show  this. 
On  treating  with  soda  faint  odors  have  been  observed  suggestive  of 
salol,  acetoacetic  ester,  pyridine,  and  anilin,  and  in  some  cases  very 
strong  and  objectionable  odors  difficult  to  describe. 
Suggested  Standard. 
The  question  now  remains  as  to  what  analytical  figures  may  be 
considered  characteristic  of  the  best  grades  on  the  market,  and  the 
following  is  suggested : 
Where  the  acid  value  is  greater  than  the  ester  value,  that  the 
difference  should  not  exceed  0.3  Cc.  iV/5  soda  per  gram  and  the 
bromine  figure  should  not  exceed  the  acid  value  by  more  than  0.15 
Cc.  in  similar  terms.  Where  the  ester  exceeds  the  acid,  the  excess 
should  not  be  more  than  0.3  Cc.  iV/5  soda  per  gram,  and  in  this  case 
the  bromine  figure  should  not  exceed  the  ester  value. 
For  free  salicylic  acid  the  limit  should  be  not  more  than  0.15  per 
cent.,  and  no  turbidity  should  occur  in  the  iron  test. 
A  good  sample  should  also  be  given  only  a  very  pale  straw  color 
when  dissolved  in  10  or  20  per  cent,  soda,  and  there  should  be  prac- 
tically no  odor  either  in  the  dry  state,  in  soda  solution,  or  when 
damped  with  spirit  and  water. 
